Stone pickers have long been used in the farming and landscaping industry to sieve through the layers of soil to separate and collect rocks and soil debris, while allowing useful topsoil to pass through and return to the top of the field. These layers of soil would be passed over a sieve formed of a series of bars which selectively allowed smaller material to pass through gaps between the bars, while keeping larger material, such as rocks, above the bars. Rotating tines aligned within the gaps between the bars would be used to then push the larger material off the surface of the sieve towards a receptacle, which could hold a large number of rocks and other material until it needed to be discarded. By removing these unwanted rocks and debris, damage to other farm machinery may be avoided and crops may experience better growing conditions.
While traditional stone sieves have proven to be very useful, they have a number of drawbacks. Sometimes, a stone enters the sieve in a “wrong” position, it may contact or direct a tine outward from an opening between the bars of the sieve. This causes the tine to make contact with at least one of bars of the sieve, which could damage the tine, bars, or both. Similarly, sometimes issues in manufacturing lead to misalignment of the tines and the bars of the sieve, such that tines may contact the bars of the sieve.